Abstract
Bat rabies cases in Europe are mainly attributed to two lyssaviruses, namely European Bat Lyssavirus 1 (EBLV-1) and European Bat Lyssavirus 2 (EBLV-2). Prior to the death of a bat worker in Finland in 1985, very few bat rabies cases were reported. Enhanced surveillance in the two subsequent years (1986–1987) identified 263 cases (more than a fifth of all reported cases to date). Between 1977 and 2016, 1183 cases of bat rabies were reported, with the vast majority (>97%) being attributed to EBLV-1. In contrast, there have been only 39 suspected cases of EBLV-2, of which 34 have been confirmed by virus typing and presently restricted to just two bat species; Myotis daubentonii and Myotis dasycneme. The limited number of EBLV-2 cases in Europe prompted the establishment of a network of European reference laboratories to collate all available viruses and data. Despite the relatively low number of EBLV-2 cases, a large amount of anomalous data has been published in the scientific literature, which we have here reviewed and clarified. In this review, 29 EBLV-2 full genome sequences have been analysed to further our understanding of the diversity and molecular evolution of EBLV-2 in Europe. Analysis of the 29 complete EBLV-2 genome sequences clearly corroborated geographical relationships with all EBLV-2 sequences clustering at the country level irrespective of the gene studied. Further geographical clustering was also observed at a local level. There are high levels of homogeneity within the EBLV-2 species with nucleotide identities ranging from 95.5–100% and amino acid identities between 98.7% and 100%, despite the widespread distribution of the isolates both geographically and chronologically. The mean substitution rate for EBLV-2 across the five concatenated genes was 1.65 × 10−5, and evolutionary clock analysis confirms the slow evolution of EBLV-2 both between and within countries in Europe. This is further supported by the first detailed EBLV-2 intra-roost genomic analysis whereby a relatively high sequence homogeneity was found across the genomes of three EBLV-2 isolates obtained several years apart (2007, 2008, and 2014) from M. daubentonii at the same site (Stokesay Castle, Shropshire, UK).
Highlights
There are currently 14 recognised species in the lyssavirus genus of the family Rhabdoviridae [1]
The genetic diversity observed for the other lyssavirus species is in contrast to the highly homogeneous sequence identities observed for European Bat Lyssavirus 2 (EBLV-2)
Evolutionary analysis was undertaken using an alignment of concatenated genes for the 29 EBLV-2 sequences
Summary
There are currently 14 recognised species in the lyssavirus genus of the family Rhabdoviridae [1]. EBLV-2 viral RNA was detected in a single oro-pharyngeal swab specimen collected from a healthy Daubenton’s bat sampled as part of an active surveillance programme in Scotland in 2008 [20]. The discovery of EBLV-2 in M. daubentonii in Finland (2009) provided evidence for the possible origin of human infection in 1985 [40] Prior to this latter case, surveillance had failed to detect EBLV-2 in Finland despite intensive efforts in 1986 by active surveillance [45] and continued passive surveillance since (albeit for low submissions averaging 10/year). In Germany, six rabies cases in Daubenton’s bats have been typed as EBLV-2 [33,34,35,41], and five genome sequences were available to be included in this study. The bat was found by a member of the public in Oppland, in the southern part of Norway [42]
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